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What  Is The California Clean Truck Check Program?

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California’s Clean Truck Check program is a statewide emissions compliance program administered by the California Air Resources Board (CARB). The program helps reduce air pollution by ensuring that heavy-duty diesel and other applicable vehicles meet California’s emissions standards.

Most heavy-duty vehicles operating in California are required to complete emissions compliance testing at scheduled intervals. Depending on the vehicle, this may include an On-Board Diagnostics (OBD) test or a J1667 Smoke Opacity Test. These tests verify that the vehicle’s emissions systems are functioning properly and that it complies with CARB regulations.

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Who Needs Clean Truck Check Testing?​

The Clean Truck Check program generally applies to heavy-duty vehicles with a gross vehicle weight rating (GVWR) of more than 14,000 pounds that operate in California, including:

  • Semi trucks

  • Box trucks

  • Diesel motorhomes and RVs

  • Buses

  • Commercial diesel vehicles

  • Fleet vehicles

Vehicle requirements and testing schedules may vary based on the vehicle’s model year and emissions equipment.

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Types of Clean Truck Check Tests​

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OBD (On-Board Diagnostics) Test

An OBD test connects directly to your vehicle’s onboard computer to verify that the emissions system is operating correctly and that there are no emissions-related faults preventing compliance.

 

J1667 Smoke Opacity Test

Older diesel vehicles that are not equipped with compatible OBD systems may require a J1667 Smoke Opacity Test. This test measures the amount of visible smoke produced during a controlled acceleration procedure to ensure emissions remain within allowable limits.

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Why Is the Program Important?

The Clean Truck Check program helps:

  • Improve California’s air quality

  • Reduce diesel emissions

  • Ensure vehicles remain environmentally compliant

  • Support healthier communities across the state

Maintaining compliance also helps vehicle owners avoid enforcement actions and keeps commercial vehicles operating legally in California.

 

 

 

How Do I Know Which Test I Need?​

The type of Clean Truck Check test required depends on your vehicle’s model year, emissions system, and CARB requirements. In general:

  • Newer heavy-duty diesel vehicles equipped with a compatible emissions control system may require an OBD (On-Board Diagnostics) Test.

  • Older diesel vehicles that do not have a compatible OBD system may require a J1667 Smoke Opacity Test.

If you are unsure which test your vehicle requires, Smog Brothers HDIM can help determine the correct testing method based on your vehicle information and ensure you complete the proper Clean Truck Check compliance test.

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